Scotty,
I have a 2016 Honda Civic Touring with the 1.5 Turbo with 120,000 miles. There is no check engine light. There are no codes with my code reader. I/M all codes completed. I was simply checking my fuel trim levels and noticed my upstream O2 sensor was high. My question is B1S1 O2 voltage is steady at 2.3 V? I thought it should be 0.1-0.9 volts. The sensor has five wires. What can it be or how do I test the sensor?
Short term and long term were both -8 to -10 percent.
Your upstream "O2' sensors are A/F sensors. (Wideband). You're thinking about narrowband O2 sensors which produce voltage signals in the 0.1-0.9 volt range (like your downstream O2 sensors).
A/F sensor "displayed" voltages @ 14.7:1 air:fuel ratio (stoichiometric) ((1.0 Lambda)) are manufacturer specific.
So (from my not so perfect memory) Toyota A/F sensors are 3.3 volts @ 1.0 Lambda.
Honda A/F sensors are 2.8 volts @ 1.0 Lambda
Also, the displayed voltages are the reverse of narrowband O2 sensors.
With narrowband O2 sensors, the higher the voltage the Richer the mixture (less O2 measured in the combustion gasses)
With wideband A/F sensors the higher the "displayed" voltage the Leaner the mixture (more O2 measured in the combustion gasses).
In your case you have -8% to -10% STFT and LTFT. You combine the STFT and the LTFT to get the total fuel trim. You're at around -20%.
And it looks like that 2.3 "displayed" voltage reading from your A/F sensor is lower than the expected 2.8 volts you'd see @ 1.0 Lambda. (it's running rich)
I put displayed voltage in quotes because that's what they are with A/F sensors.
A/F sensors don't produce voltage signals. They operate on current signals. They're just displayed as voltage values on a scanner.
Thank you for the help.